Fire stop between floor slab and curtain wall of building

ABSTRACT

A fire stop separating superposed floors of a building having a concrete floor slab and a curtain wall horizontally separated by a gap to permit relative thermal expansion movement of the slab and wall essentially consists of a trough of pliable sheet steel filling the gap, and urea formaldehyde resin foam filling the upwardly open cavity of the trough. The foam chars, but does not burn in the event of a fire so as to retain its cellular structure and much of its thermal insulating properties, and the thin sheet steel can support the light foam and its own weight even at temperatures high enough to reduce the tensile strength of the steel.

Kramer [451 Jan. 22, 1974 FIRE STOP BETWEEN FLOOR SLAB AND CURTAIN WALLOF BUILDING Inventor: Fritz Kramer, Woodside, N.Y.

Assignee: U. F. Chemical Corp., Woodside,

Filed: Dec. 6, 1971 Appl. No.: 205,106

US. Cl 52/232, 52/284, 52/317, 52/573 Int. Cl. E04c 2/00, E04b 1/74Field of Search..... 52/232, 259, 309, 317, 573; 117/137 ReferencesCited UNITED STATES PATENTS 9/1912 l-lansbrough ..52/259 8/1942 Fletcher117/136 2,616,866 11/1952 Juda 117/136 Primary Examiner-Henry C.Sutherland Assistant Examiner-James L. Ridgill, Jr.

Attorney, Agent, or Firm-Kurt Kelman et a1.

[5 7] ABSTRACT A fire stop separating superposed floors of a buildinghaving a concrete floor slab and a curtain wall horizontally separatedby a gap to permit relative thermal expansion movement of the slab andwall essentially consists of a trough of pliable sheet steel filling thegap, and urea formaldehyde resin foam filling the upwardly open cavityof the trough, The foam chars, but does not burn in the event of a fireso as to retain its cellular structure and much of its thermalinsulating properties, and the thin sheet steel can support the lightfoam and its own weight even at temperatures high enough to reduce thetensile strength of the steel.

5 Claims, 1 Drawing Figure FIRE STOP BETWEEN FLOOR SLAB AND CURTAIN WALLOF BUILDING This invention relates to fireproof building construction,and particularly to a fire stop for insulating the floors of a buildingfrom each other in the event of a Modern office buildings and likestructures have concrete floor slabs and upright curtain walls ofconcrete or metal which must be spaced apart slightly to allow fordifferential thermal expansion. A gap approximately 2-4 inches wideextends along the outer edges of each slab and connects the floors aboveand below, and must be plugged by a fire stop to prevent propagation offires between the floors. However, the fire stops employed heretoforeprovide protection for only limited periods, and recent fires are knownto have burned through many floors of supposedly fireproof, newlyerected buildings of the type described within a fraction of whombecause of the inadequacy of the conventional fire stops.

It has now been found that a fire stop consisting of a body ofurea-formaldehyde resin foam supported on a shell of sheet steel thinenough to be pliable, yet strong enough to carry its own weight and thatof the supported, light resin foam when installed in the gap between aconcrete floor slab and an upright curtain wall is more durable in theevent of a fire than the materials employed heretofore. The fire stop ofthe invention does not load the structure with a significant burden,costs very little, and is as durable as any other material ofconstruction whenprotected againstrust, the resin foam being unaffectedby atmospheric conditions and parasites.

The fire stop of the invention consists of a trough member of metallicmaterial secured in the gap btween a slab element and a wall element ofthe building to be protected and extending substantially from the innerface of the wall element to the edge face of the floor slab. Theupwardly open cavity of the trough is substantially completely filled bya body of urea formaldehyde resin foam. I

Other featues and many of the attendant advantages of this inventionwill readilybecome apparent as the same becomes better understood byreference to the following detailed description of preferred embodimentswhen considered inconnection with the appended drawing in which the soleFIGURE shows a building including a fires top of the invention inelevational section.

The drawing shows only as much of a high-rise office building as isneeded for an understanding of this invention, the remainder of thebuilding being either conventional or duplicaTing the illustratedfeatures of the invention.

The floor slab l of reinforced concrete separates an upper floor from alower floor, the floors not being shown in detail, and is separatd froma curtain wall 2 by an air gap. An elongated trough 3 of galvanized mildsteel sheet extends along the entire air gap between the inner face 4 ofthe curtain wall 2 and the narrow edge face 5 of the floor'slab 1.

The trough 3 is of approximately U-shaped cross section, and the legportions 6, 7 of the U-shape abuttingly engage the faces 4, 5respectively. A wide, flat lip portion 8 integral with the leg portion 7engages the up wardly directed major surface 9 of the slab 1 in areacontact. In the structure so far described, the troughv 3 foam isrelatively low, and that of charred foam is even is fulcrumed on theupper free edge of the slab 1, cannot pivot clockwise because of theabutting engagement of the leg portion 6 with the inner face 4, norcounterclockwise because of engagement of the lip portion 8 with theupwardly directed surface 9 of the slab 1.

A body 10 of urea-formaldehyde resin foam fills the upwardly openreceptacle provided by the cavity of the trough 3 and overflows thereceptacle to a small extent.

The fire stop essentially constituted by the trough 3 and the foam body10 is installed by first cutting thin, glavanized sheet steel to thedesired size, then bending it into the J-shape of a trough fittingbetween the faces 4, 5 under resilient compressive stress and ultimatelyfolding the longer leg of the J-shape over the edge of the slab 1 toform the lip 8. If so desired, the steel sheet may be fastenedtemporarily to the wall face 4 and/or the upper slab surface 9 by dropsof quick-curing epoxy cement or by means of adhesive tape to facilitatethe bending operation in which the elements of the building itself areemployed as bending forms. The only tool required is a pair of tinsnipsor strong scissors for cutting the sheet steel employed which may nothave to be thicker than 2 mils, and is strong enough even under adverseconditions when it is 5 mils thick. Steel heavier than 0.0l0 inch isneither necessary nor even desirable under any conditions that I ampresently aware of.

Urea formaldehyde resin foam is prepared from ureaformaldehydeprecondensate, compressed air, a surfactant, water, and phoshporic acidas a catalyst in a conventional manner, using the foam generator ofBauer, U.S. Pat. No. 2,860,856 or equivalent equipment. The foam is softwhen ejected from the nozzle of the generator which is directed towardthe open top of the trough 3. The fresh foam confonns to the trough soas fully to occupy the receptacle available, and is preferably appliedin a thickness of at least 4 inches and in slight excess so that itoverflows the trough 3 and plugs any cracks that may exist between thetrough 3 and the cooperating building elements 1, 2. The'foam quicklysolidifies and reaches its ultimate mechanical strength within a fewdays.

In the event of a fire, there is no significant amount of perishablematerial in the fire stop. The steel sheet is strong enough to carry itsown weight and that of the foam (approximately 0.6 lbs/cu. ft.) even ifheated close to its softening temperature, an unlikely event. Theurea-formaldehyde foam chars gradually and without giving off noxious orcombustible vapors when heated beyond its decomposition temperature. Ifhigh enough a temperature is maintained long enough, the foam isconverted into a cellular carbon body which stills traps air in itscells and thus provides thermal insulation between the two floorsseparated by the slab l. The gap between the faces 4, 5 remains sealedregardless of thermally induced relative movement of the buildingelements 1, 2 during fire on the lower floor. The fire thus cannot makeits way from the lower to the upper floor along the curtain wall 2 whichis coextensive with both floors.

The mechanical strength of urea-formaldehyde resin lower. The foam body10, however, is not subjected to significant mechanical stresses duingits use in a fire.

stop, and the minimal stresses applied are born by the sheet steel. Boththe trough 3 and the foam [0 are resilient enough to absorb the changesin the width of the gap between the faces 4, 5 due to thermal expansionand contraction of the structural elements 1, 2.

Galvanized sheet steel is preferred because of ther rust protectionafforded by the zinc coating, but phosphate conversion coatings and likesurface treatments may be resorted to in a known manner.

Other metals may be substituted for steel if so desired. Aluminum andits alloys, however, have been found to have melting points too low forperforming the intended task, and any metal other than steel andemployed for making the trough 3 should have a melting point well abovethat of aluminum.

No full adequate plastic foam is available at this time to replace theurea-formaldehyde foam described above. Some plastic foams, such aspolyurethane foam, are flammable, and others give off noxious or eventoxic vapors, as in the case of phenol-formaldehyde resin foam.Urea-formaldehyde resin foam is most economical at this time, and thecost of the fire stops of the invention is minimal both in materials andin labor required for installation.

The particular trough illustratd has been found most convenient becauseof its ability to be shaped at the site by unskilled or semi-skilledworkmen without special tools, but modifications of the trough willreadily suggest themselves for specific applications. If the leg portion6 is fastened initially to the wall face 4, it is not necessary toattach the lip portion 8 to the slab surface 9. When the gap between thefaces 4, 5 widens due to thermal stresses or otherwise, the lip portion8 may then slide freely on the slab surface 9.

It should be understood, therefore, that the foregoing disclosurerelates only to a preferred embodiment of the invention and that it isintended to cover all changes and modifications in the example of theinvention -herein chosen for the purpose of the disclosure which do notconstitute departures from the spirit and scope of the invention setforth in the appended claims.

What is claimed is:

1. In a building having a horizontal slab element separting a lowerfloor of the building from an upper floor, said slab element having twomajor surfaces respectively directed toward said floors and an edge faceconnecting said major surfaces, a wall element having an inner uprightface adjacent said edge face, said faces defining a gap therebetween topermit limited relative movement of said faces in a horizontaldirection, said gap connecting said floors, and a fire stop in said gap,the improvement in the fire stop which comprises:

a. a trough member of resilient sheet steel having a thickness of 0.002to 0.010 inch secured in said gap and extending substantially from oneof said faces to the other face,

1. said trough member defining an upwardly open receptacle; and

b. a body of urea-formaldehyde resin foam substantially filling saidreceptacle,

1. whereby said trough member and said foam absorb the changes in thewidth of said gap between said faces due to thermal expansion andcontraction of said elements.

2. In a building as set forth in claim 1, said trough member beingsecured to one of said elements and having a lip portion engaging theother element.

3. In a building as set forth in claim 2, said one element being saidwall element and said lip portion engaging the major surface of saidslab element directed toward an upper floor.

4. In a building as set forth in claim 2, said trough member being ofarcuate cross section in a vertical plane perpendicular to said innerface.

5. In a building as set forth in claim 2, said lip portion being planarand substantially parallel to the engaged surface of said slab element.

2. In a building as set forth in claim 1, said trough member beingsecured to one of said elements and having a lip portion engaging theother element.
 3. In a building as set forth in claim 2, said oneelement being said wall element and said lip portion engaging the majorsurface of said slab element directed toward an upper floor.
 4. In abuilding as set forth in claim 2, said trough member being of arcuatecross section in a vertical plane perpendicular to said inner face. 5.In a building as set forth in claim 2, said lip portion being planar andsubstantially parallel to the engaged surface of said slab element.